The invention relates generally to power-driven modular plastic conveyor belts and, more particularly, to modular plastic conveyor belts hingedly interconnected row to row by non-circular hinge pins.
Conventional modular conveyor belts and chains are constructed of modular links, or belt modules, arranged in rows. Spaced apart hinge eyes extending from each end of the modules include aligned openings. The hinge eyes along one end of a row of modules are interleaved with the hinge eyes of an adjacent row. A pivot rod, or hinge pin, journalled in the aligned openings of interleaved hinge eyes, connects adjacent rows together end to end to form an endless conveyor belt capable of articulating about a drive sprocket or drum.
Because they do not corrode and are easy to clean, modular plastic conveyor belts are often used instead of metal belts. Usually, the hinge pins in plastic belts are also made of plastic. The hinge pins are typically circular in cross section and reside in circular openings in the hinge eyes. Relative motion between the hinge pins and the walls of the hinge eyes as the belt articulates about sprockets tends to wear both the hinge pin and the hinge eye wall. In abrasive environments, such as in conveying potatoes and other agricultural produce, this wear is accelerated by the intrusion of dirt and grit into the hinges of the belt.
Metal hinge pins are sometimes used to increase the wear life of the pins. But that does not do away with the relative motion between pin and hinge eye wall, and belt module wear at the hinge is still a problem.
Non-circular hinge strips made of a flexible material have been proposed to resist wear. Hinge eyes forming slots with flared ends permit the confined hinge strip to flex a limited angle without frictionally rubbing with the hinge eyes as the belt articulates. Such an arrangement is effective in increasing wear life, but the flexible hinge strip is inherently weak in shear strength and unsuitable for carrying heavy loads.
Some power transmission chains constructed of metal components use a pair of pins in each joint between consecutive groups of links. At each joint, one pin is wedged into the openings of one group of links and another pin, in rocking engagement with the first pin, is wedged in the openings of the adjacent group of links. In this way, relative motion is confined to the rocking surfaces of the metal pins. But transmission chains and modular conveyor belts operate in different environments and serve different purposes. Power transmission chains often are used in well-lubricated environments, relatively free of abrasives, as in internal combustion engines and other machinery in which the use of gears is impractical. Modular conveyor belts, on the other hand, are frequently used in very abrasive, non-lubricated environments to move various products over long distances.
Thus, there is a need for a modular plastic conveyor belt that can resist wear at the hinge for a long operating life even in abrasive environments.